I. Field of the Invention
The present invention relates generally to turbine engine lubrication systems and, more particularly, to such a system which utilizes the turbine engine fuel as the lubricant.
II. Description of the Prior Art
Gas turbine engines typically include a main shaft rotatably supported by a bearing assembly in a support housing which is stationary relative to the main shaft. The main shaft rotates at high rotational speeds thus requiring that the bearing assembly be constantly and adequately lubricated. Without adequate lubrication, the bearing assembly can seize or otherwise fail which renders the turbine engine inoperable and may even result in the destruction of the turbine engine.
There have been many previously-known turbine engine lubrication systems which employ a high-grade oil as the lubricant. While these previously-known lubrication systems vary in precise construction between each other, typically an oil pump, situated within the support housing, continuously pumps oil to the bearing assembly by one or more jets which direct the oil into the bearing assembly, or by radial ports formed in one or both of the bearing races of the bearing assembly. These previously-known oil pumps can be electrically, pneumatically or hydraulically powered, but typically are rotatably driven by a gear arrangement mechanically coupled to the main shaft of the turbine engine. After passing through the bearing assembly, the oil is collected in a reservoir formed in the bottom of the bearing cavity and is subsequently cooled, filtered, and recirculated through the bearing assembly by the oil pump.
These previously-known turbine engine lubrication systems, however, are disadvantageous for a number of reasons. First, the previously-known turbine lubrication systems are expensive in construction due not only to the cost of the oil pump, but also in the cost of the associated oil reconditioning systems, and the means for driving the oil pump. In addition, the oil pumps and their associated components are bulky and heavy in construction and thus present a design problem for the turbine engine.
A still further disadvantage of these previously-known turbine lubrication systems is that such systems, and particularly the oil pump, are prone to failure. Upon such failure, of course, the oil is no longer pumped to the bearing assembly so that the bearings rapidly heat up and fail. As previously mentioned, the failure of the bearing assembly can result in the destruction of the turbine engine.
A still further disadvantage of these previously-known turbine lubrication systems is that the oil is collected in a reservoir formed in the bearing cavity for recirculation by the oil pump through the bearing assembly. Collection or accumulation reservoirs must be provided to accommodate any orientation of the turbine engine with respect to the vertical. In order to ensure that the oil can be returned to the pump for recycling each additional accumulation reservoir requires a separate pump element to return the oil to the pump or main storage reservoir and the additional expense and complexity adversely affects both the cost and the reliability of the overall lubrication system.